As is known in the related art, a fly sewing machine includes a fly supply unit which supplies flies from the upstream side along a fly transfer passage which is provided on a stand, a fly feed unit which sequentially transfers the flies supplied by the fly supply unit, a transfer speed-adjusting part which sends the flies transferred by the fly transfer unit to a sewing machine part in the downstream side at required timing, and a chain feed unit provided between the transfer speed-adjusting part, the chain feed unit sending a continuous slide fastener chain to the sewing machine part in synchronization with the sewing speed of the sewing machine part (e.g., refer to Patent Document 1).